Useful high dye-yield (HDY) couplers have been disclosed by Moobenry and Singer in U.S. Pat. No. 4,840,884. Such couplers react with oxidized color developer to form one dye and in doing so release a precursor of a second dye. The patent provides examples (Example 38 and 40) of hydrophilic sulfonamide solubilization of the coupler. Example 39 incorporates a sulfonamide in the coupler as well as carboxyl solubilization in the dye moiety for enhanced reactivity. It has been found, however, that couplers of this type, particularly those containing a coupler portion capable of forming a yellow dye upon coupling with oxidized developer, are often unsatisfactory from the standpoint of reactivity.
Reactivity improvements can be obtained in couplers of this type which contain timing groups as disclosed in U.S. Pat. No. 5,447,819. These couplers have the general formula COUP--(T).sub.m --L--DYE and particular solubilizing groups are incorporated in the timing group (T) to enhance reactivity. It has been found however that such couplers containing a timing group present other problems. In particular, such couplers have been found to cause dark keeping problems. It is believed that the described high dye-yield coupler can be unstable during keeping and can be oxidized in ambient surroundings. This oxidation results in the release of the DYE portion of the coupler which then shifts from colorless to yellow colored and this is an unacceptable result.
U.S. Pat. No. 5,457,004 describes high dye yield couplers having methine dye chromophores. Several of the described couplers (I-4, I-5, I-46, I-57 and I-60) disclose acyloxy links between the COUP and DYE groups. All contain sulfonamide-solubilized coupler moieties. Example I-60 incorporates a carboxyl group in the dye moiety as well. The sulfonamide couplers have proved to be less reactive than desired toward color developer.
A problem to be solved is to provide a silver halide photographic element containing a stable high dye-yield coupler that will exhibit a higher reactivity with oxidized developer than couplers heretofore discovered.